Photochromic compound, process for production thereof, use thereof and composition containing said photochromic compound

ABSTRACT

A photochromic compound represented by the following general formula [I] ##STR1## wherein ##STR2##  represents a divalent aromatic hydrocarbon group or a divalent heterocyclic group each of which may have a substituent, 
     R 1  represents a monovalent hydrocarbon group or a monovalent heterocyclic group each of which may have a substituent, ##STR3##  represents a norbornylidene or adamantylidene group which may have a substituent, 
     X represents an oxygen atom or a group of the formula &gt;N--R 3  in which R 3  represents a hydrogen atom or a hydrocarbon group which may have a substituent, and 
     R 2  represents a monovalent hydrocarbon group which may have a substituent. 
     Also provided are a process for production of the photochromic compound, a composition containing the photochromic compound, and the use of the photochromic compound. The colored form of this photochromic compound has excellent thermal stability.

This invention relates to a novel compound having a photochromic action, processes for producing it, a composition comprising it, and its use. More specifically, it relates to a novel compound which changes reversibly in color from a colorless form to a colored form by the action of light containing ultraviolet rays such as sunlight or the light from a mercury lamp and has excellent thermal stability in colored form, processes for its production, a composition comprising it, and to

Photochromism, which has aroused a particular interest for the last several years, denotes a phenomenon in which when light containing ultraviolet rays such as sunlight or the light from a mercury lamp is irradiated onto a certain compound, its color rapidly changes, and when the light irradiation is stopped and the compound is placed in a dark place, its color reversibly returns to the original color. Compounds having this property are called photochromic compounds. Photochromic compounds of various structures have been synthesized and proposed, but no particular common structure has been observed in these compounds.

Compounds represented by the following general formula ##STR4## wherein ##STR5## represents a substituted or unsubstituted adamantylidene group, R' represents a hydrogen atom, an alkyl group, an aryl group, an aralkyl group or a heterocyclic group, X' represents oxygen or the group >N--R" in which R" represents a hydrogen atom, an aryl group, an alkyl group or an aralkyl group, and ##STR6## represents an aromatic group or an unsaturated heterocyclic group, are known as a series of photochromic compounds which absorb ultraviolet rays and are colored and rapidly return to their original color under white light (U.S. Pat. No. 4,220,708). These compounds are not at all colored, or hardly colored, under sunlight because they show a tendency to returning to a colorless form under white light. Furthermore, these compounds have the property of being thermally stable and not returning to the colorless form at room temperature and their use as a photomemory material by utilizing this property has recently been actively exploited. However, because the repetition life of their photochromism is short, they have not yet come into commercial acceptance.

Compounds of the above formula are known to be converted by heating into photochromic compounds of the following general formula which are colored under sunlight (see U.K. Patent Application No. 2,146,327) ##STR7## wherein ##STR8## R', X' and ##STR9## are the same as defined with regard to the above compounds.

It is believed that since the above photochromic compounds have rigid non-flexible cage-like adamantylidene groups, the single bond forming part of the six-membered ring is weakened and an electron cyclic ring-opening by irradiation of solar light is facilitated and consequently, the compounds become colored. However, the colored form of the above compound is thermally unstable and at room temperature and it completely returns to the colorless form in several seconds to several minutes. Hence, there is little possibility that these compounds will be used as photomemory material.

It has been desired therefore to develop photochromic compounds which reversibly repeat color formation and extinction over an extended duration, and have excellent thermal stability in the colored form, and which can be used as photomemory materials.

It is an object of this invention to provide a novel photochromic compound.

Another object of this invention is to provide a compound which reversibly changes from a colorless form to a colored form by the action of ultraviolet rays.

Still another object of this invention is to provide a photochromic compound having durability which can be used for a long period of time.

Yet another object of this invention is to provide a photochromic compound having practical utility.

A further object of this invention is to provide industrially advantageous processes for producing the photochromic compound.

A still further object of this invention is to provide a polymeric composition comprising the photochromic compound, and a photomemory material composed of the composition.

Other objects of the invention will become apparent from the following description.

These objects and advantages of this invention are achieved by a novel compound represented by general formula [I] ##STR10## wherein ##STR11## represents a divalent aromatic hydrocarbon group or a divalent heterocyclic group each of which may have a substituent,

R₁ represents a monovalent hydrocarbon group or a monovalent heterocyclic group each of which may have a substituent, ##STR12## represents a norbornylidene or adamantylidene group which may have a substituent,

X represents an oxygen atom or a group of the formula >N--R₃ in which R₃ represents a hydrogen atom or a hydrocarbon group which may have a substituent, and

R₂ represents a monovalent hydrocarbon group which may have a substituent.

The compound of general formula [I] provided by this invention will be described in detail.

In general formula [I], ##STR13## is a norbornylidene or adamantylidene group which may have a substituent. The norbornylidene group is represented by the following formula. ##STR14## The adamantylidene group is represented by the following formula. ##STR15##

The above formulae show the skeletal structures of the norbornylidene group and the adamantylidene group having no substituent. One or more hydrogen atoms in the above formulae may be substituted by a substituent. The types and number of such substituents and the substitution positions may be selected according to the purpose and utility. When the norbornylidene or adamantylidene group has a plurality of substituents, they may be of the same or different kinds.

The suitable number of substituents, if present, is generally 1 to 5, preferably 1 to 3.

Examples of the substituents for the norbornylidene or adamantylidene group include a hydroxyl group, a nitro group, a cyano group, a carboxyl group, halogen atoms (e.g., fluorine, chlorine and bromine), alkylamino groups having 1 to 4 carbon atoms (e.g., methylamino or ethylamino), di(C₁ -C₄)alkylamino groups (e.g., dimethylamino or diethylamino), C₁ -C₄ alkyl groups (e.g., methyl, ethyl, propyl and t-butyl), C₁ -C₄ alkoxy groups (e.g., methoxy, ethoxy, propoxy and t-butoxy), C₁ -C₂ haloalkyl groups (e.g., chloromethyl, trichloromethyl or trifluoromethyl), C₂ -C₁₀ alkoxycarbonyl groups (e.g., methoxycarbonyl, ethoxycarbonyl and butoxycaronyl), (C₁ -C₄)alkylcarbonyl(C₁ -C₄)alkyl groups (e.g., methylcarbonylmethyl and methylcarbonylethyl), C₇ -C₉ aralkyl groups (e.g., benzyl, phenylethyl and phenylpropyl), C₇ -C₁₅ aralkoxy groups (e.g., benzyloxy and phenylethoxy), C₆ -C₁₀ aryl groups (e.g., phenyl, tolyl naphthyl), and C₆ --C₁₀ aryloxy groups (e.g., phenoxy and 1-naphthoxy).

Of these substituents, the halogen atoms, the C₁ -C₄ alkyl groups, the C₁ -C₄ alkoxy groups, the C₁ -C₄ alkylamino groups, the di(C₁ -C₄)alkylamino groups and the (C₁ -C₄)alkylcarbonyl(C₁ -C₄)alkyl groups are preferred.

As ##STR16## the adamantylidene group which have a substituent is preferable to the norbornylidene group which may have a substituent because of higher thermal stability. When ##STR17## is an adamantylidene group which may have a substituent and X is an oxygen atom, a thermally stable colored form of photochromic compound can be obtained. Accordingly this combination is especially preferred.

When X is the group >N--R₃, R₃ is a hydrogen atom or a hydrocarbon group which may have a substituent. The hydrocarbon group is preferably a C₁ -C₄ alkyl group, a C₅ -C₇ cycloalkyl group, a C₇ -C₁₀ aralkyl group or a C₆ -C₁₀ aryl group. Specific examples include alkyl groups having 1 to 6 carbon atoms such as methyl, ethyl, propyl, n-butyl, iso-butyl and n-hexyl groups; cycloalkyl groups having 5 to 7 carbon atoms such as cyclopentyl and cyloheptyl groups; aralkyl groups having 7 to 10 carbon atoms such as benzyl, phenylethyl and phenylpropyl groups; and aryl groups having 6 to 10 carbon atoms such as phenyl, naphthyl, tolyl and xylyl groups.

These hydrocarbon groups may each be substituted by at least one atom or group selected from the class consisting of halogen atoms, a cyano group, a nitro group, a hydroxyl group, C₁ -C₆ alkoxy groups, C₆ -C₁₀ aryloxy groups, ##STR18##

In these formulae, R₄ represents a C₁ -C₄ alkyl group or a C₆ -C₁₀ aryl group which may each be substituted by a halogen atom. R₅ is a C₁ -C₄ alkyl may be substituted by a halogen atom or a nitro group, or a C₆ -C₁₀ aryl group which may be substituted by a cyano group, or a C₇ -C₁₀ aralkyl group. R₆ and R₇ are identical or different, and each represents a hydrogen atom, a C₁ -C₄ alkyl group, a C₇ -C₁₀ aralkyl group or a C₆ -C₁₀ aryl group. In the above substituents, examples of the halogen atoms are fluorine, chlorine, bromine and iodine atoms. Examples of the C₁ -C₆ alkoxy groups include methoxy, ethoxy, propoxy and butoxy groups. The C₆ -C₁₀ aryloxy groups are, for example, phenoxy, naphthoxy and tolyloxy groups. The C₆ -C₁₀ aryl groups are, for example, phenyl, naphthyl and tolyl groups. Examples of the C₇ -C₁₀ aralkyl groups are benzyl, phenylethyl and phenylpropyl groups.

Usually 1 to 5, preferably 1 to 3, such substituent, may be substituted on the above hydrocarbon groups. When there are two or more substituents, they may be identical or different.

When X is the group >N--R₃, R₃ is preferably a C₁ -C₆ alkyl group, a C₅ -C₇ cycloalkyl group or a C₇ -C₁₀ aralkyl group each of which may be substituted by a halogen atom, a cyano group, a nitro group, a C₁ -C₆ alkoxy group or the ##STR19## in which R₅ is a C₁ -C₄ alkyl group which may be substituted by a halogen atom or a nitro group, or a C₆ -C₁₀ aryl group which may be substituted by a cyano group.

In general formula [I], R₁ represents a monovalent hydrocarbon group or a monovalent heterocyclic group each of which may be substituted. The monovalent hydrocarbon group for R₁ may be an aliphatic, alicyclic or aromatic hydrocarbon group, preferably a C₁ -C₂₀, especially C₁ -C₆, alkyl group such as methyl, ethyl, propyl and butyl groups, a C₆ -C₁₀ aryl group such as phenyl, tolyl, xylyl and naphthyl groups, or a C₇ -C₁₀ aralkyl group such as benzyl, phenylethyl, phenylpropyl and phenylbutyl groups.

The monovalent heterocyclic group for R₁ is preferably a 5- or 6-membered monoheterocyclic group having 1 to 3, preferably 1 or 2, hetero atoms selected from nitrogen, oxygen and sulfur atoms, or a fused heterocyclic group resulting from fusion of a benzene ring thereto. Specific examples of the heterocyclic group include nitrogen-containing heterocyclic groups such as pyrrolyl, pyridyl, quinolyl and piperidyl groups, oxygen-containing heterocyclic groups such as furyl, benzofuryl and oxolanyl groups, and sulfur-containing heterocyclic groups such as benzothienyl and thiolanyl groups.

The hydrocarbon group or heterocyclic group for R₁ may have a substituent. The number of such substituents on R₁ is at most 5, preferably at most 3. Specific examples of the substituents may be the same as given above with regard to ##STR20##

Examples of preferred R₁ groups include C₁ -C₆ alkyl groups which may be substituted by a halogen atom pr a C₁ -C₄ alkoxy group; C₇ -C₁₀ aralkyl groups which may be substituted by halogen atoms; C₆ -C₁₀ aryl groups which may be substituted by a halogen atom, a nitro group or a C₁ -C₄ alkoxy group; 5- or 6- membered monoheterocyclic groups containing 1 to 3 hetero atoms; and fused heterocyclic groups resulting from fusion of a benzene ring to the above monoheterocyclic groups.

Especially preferred R₁ groups are C₁ -C₆ alkyl groups, C₇ -C₁₀ aralkyl groups, and C₆ -C₁₀ aryl groups which may be substituted by a halogen atom, a nitro group or a C₁ -C₄ alkoxy group.

R₂ in general formula [I] in this invention is a monovalent hydrocarbon group which may have a substituent. That R₂ is a monovalent hydrocarbon which may be substituted is of great technical significance to the thermal stability of the colored form of the compound of formula [I]. In this case, the colored form of the compound [I] has much improved thermal stability over the case in which R₂ is not a hydrocarbon (R₂ is a hydrogen atom). Accordingly, the compounds of this invention can be used as a photomemory material.

R₂ in general formula [I] is preferably a C₁ -C₆ alkyl group, a C₅ -C₇ cycloalkyl group, a (C₅ -C₇) cycloalkyl(C₁ -C₄)alkyl group, a C₇ -C₁₀ aralkyl group, or a C₆ -C₁₀ aryl group. Each of these groups may be substituted by a halogen atom, a cyano group, a nitro group, a hydroxyl group, a C₁ -C₆ alkoxy group, a C₆ -C₁₀ aryloxy group which may be substituted by a halogen atom, a C₇ -C₁₀ aralkoxy group, the ##STR21## The number of such substituents may be 1 to 5, preferably 1 to 3. When there are two or more substituents, they may be of the same or different kind. In the above substituents, R₄, R₅, R₆ and R₇ are the same as defined above with regard to >N--R₃.

Specific preferred examples of R₂ and substituents on it include C₁ -C₆ alkyl groups such as methyl, ethyl, propyl, n-butyl, iso-butyl, t-butyl, n-pentyl and iso-pentyl groups; C₅ -C₇ cycloalkyl groups such as cyclopentyl, cyclohexyl and cycloheptyl groups, (C₅ -C₇)cycloalkyl(C₁ -C₄)alkyl groups such as cyclohexylmethyl and cyclohexylethyl groups; C₇ -C₁₀ aralkyl groups such as benzyl, phenylethyl and phenylpropyl groups; C₆ -C₁₀ aryl groups such as phenyl, naphthyl, tolyl and xylyl groups; halogen atoms such as fluorine, chlorine and iodine atoms; C₁ -C₆ alkoxy groups such as methoxy, ethoxy, propoxy and butoxy groups; C₆ -C₁₀ aryloxy groups such as phenoxy, naphthoxy and tolyloxy groups; and C₇ -C₁₀ aralkoxy groups such as benzyloxy and phenylethoxy groups.

The above monovalent hydrocarbon groups other than the C₆ -C₁₀ aryl groups are preferred as R₂. ##STR22## in general formula [I] represents a divalent aromatic hydrocarbon group or a divalent heterocyclic group each of which may have a substituent. The aromatic hydrocarbon group preferably has 6 to 14 carbon atoms, specifically a phenylene, napthalene or phenanthrene group. The heterocyclic group is preferably a 5- or 6-membered monoheterocyclic group having 1 to 3, preferably 1 or 2 hetero atoms selected from nitrogen, oxygen and sulfur atoms. Specific examples of the heterocyclic group are furanyl, pyrrolyl, thiophenyl, benzofuranyl, indolyl and benzothiophenyl groups.

The aromatic hydrocarbon group or heterocyclic group may each have at least one substituent selected from halogen atoms, nitro groups, cyano groups, C₁ -C₄ alkyl groups, C₁ -C₄ alkylamino groups, di(C₁ -C₄)alkylamino groups, phenyl groups and C₁ -C₄ alkoxyphenyl groups. The number of these substituents may be 1 to 5, preferably 1 to 3. When there are two or more substituents, they may be identical or different. When two alkyl groups are substituted, they may be bonded to each other to form a ring.

In the substituents on the aromatic hydrocarbon group or the heterocyclic group in ##STR23## examples of the halogen atom are fluorine, chlorine, bromine and iodine atoms. Examples of C₁ -C₄ alkoxy groups are methoxy, ethoxy, propoxy and butoxy groups. Examples of C₁ -C₄ alkylamino groups are methylamino, ethylamino and butylamino groups. Examples of the di(C₁ -C₄)alkylamino groups are dimethylamino, diethylamino, methylethylamino, dipropylamino and dibutylamino groups.

Preferred examples of ##STR24## include a divalent benzene ring, a divalent naphthalene ring, a divalent furan ring, a divalent pyrrole ring, a divalent thiophene ring, a divalent benzofuran ring, a divalent indole ring, a divalent benzothiophene ring and a divalent tetrahydrobenzothiophene ring. These rings may be substituted by an atom or group selected from the class consisting of halogen atoms, nitro groups, cyano groups, C₁ -C₄ alkyl groups, C₁ -C₄ alkoxy groups, C₁ -C₄ alkylamino groups, di(C₁ -C₄)alkylamino groups, phenyl groups and C₁ -C₄ alkoxyphenyl groups.

Most preferred compounds of this invention are those of general formula [I] in which

X is an oxygen atom or the group >N--R₃ wherein R₃ represents a C₁ -C₆ alkyl group which may be substituted by a halogen atom, a cyano group, or a C₂ -C₅ alkoxycarbonyl group, ##STR25## represents a norbornylidene or adamantylidene group,

R₁ represents a alkyl group or a C₆ -C₁₀ aryl group,

R₂ is a C₁ -C₄ alkyl group which may be substituted by a C₂ -C₅ alkoxycarbonyl group, and ##STR26## is a divalent furan ring, a divalent pyrrole ring or a divalent thiophene ring.

The compound of general formula [I] may be produced by any manufacturing process, and is not limited by the type of the manufacturing process. Preferred typical processes are described below without any intention of limiting the invention thereby.

Typically, the compound of general formula [I] can be obtained by reacting a compound represented by the following general formula [II] ##STR27## wherein ##STR28## and X are as defined in general formula [I], with a halogen compound represented by the following general formula [III]

    Hal--R.sub.2                                               [III]

wherein Hal represents a chlorine, bromine or iodine atom, and R₂ is as defined in general formula [I], in the presence of an alkali metal or an alkali metal carbonate or after the compound of general formula [I]is reacted with the alkali metal or its carbonate.

The alkali metal used in this process may be, for example, sodium, potassium or lithium. Examples of the alkali metal carbonate are sodium carbonate, potassium carbonate and lithium carbonate. The proportion of the alkali metal or its carbonate is 10 to 20 moles per mole of the compound of general formula [II]. The proportion of the halogen compound of general formula [III] is 0.5 to 20 moles per mole of the compound of formula [II].

Preferably, this reaction is carried out by using a solvent. Examples of the solvent that can be preferably used include polar aprotic solvents such as dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, hexamethylphosphoric triamide, tetrahydrofuran and 1,4-dioxane.

The reaction is carried out at a temperature of usually 0° to 200° C., preferably 0° to 50° C. for a period of 1 to 170 hours, preferably 5 to 50 hours under a pressure from normal atmospheric pressure to 5 atmospheres, preferably atmospheric pressure to 3 atmospheres. After the reaction, the solvent is removed, and the product is dissolved in a solvent such as diethyl ether. The insoluble alkali metal halide, etc. are removed by filtration. The residue is purified by silica gel chromatography using a solvent such as chloroform or dichloromethane as an eluent to give the desired product.

In the above process, there can be employed a procedure in which the compound of general formula [II] is first reacted with the alkali metal or its carbonate, and then with the halogen compound of general formula [III]. This is not limitative, however. For example, when the compound of general formula [II], the alkali metal or its carbonate, and the halogen compound of general formula [III] are simultaneously contacted, the above consecutive reactions proceeded and the compound of general formula [I] of the invention can be obtained.

The compound of general formula [I] generally exists as a pale yellow solid at room temperature, and can generally be identified by the following procedures (a) to (c).

(a) The types and number of protons existing in the molecule can be determined by measuring the proton nuclear magnetic resonance spectrum (H¹ -NMR) of the compound. Specifically, in the H¹ -NMR spectrum, there appear a peak based on aromatic protons near δ7-8 ppm, a broad peak based on protons derived from the adamantylidene or norbornylidene group near δ1.2-2.5 ppm, and a peak based on the alkyl group in R¹ near δ1.2-4.0 ppm (where R₁ is an alkyl group). By comparing the intensities of these peaks, the number of protons of the bonding groups can be determined.

(b) By elemental analysis, the weight percentages of carbon, hydrogen, nitrogen, sulfur and halogen can be determined. The weight percent of oxygen can be calculated by subtracting the total weight percentage of the elements from 100. Accordingly, the composition of the product can be determined.

(c) The types of carbons present in the molecule can be determined by measuring the ¹³ C-nuclear magnetic resonance spectrum of the compound. There appear a peak derived from carbons of the adamantylidene or norbornylidene group near δ27-52 ppm, a peak based on carbons of the alkyl group in R₁ near δ15-35 ppm (where R₁ is an alkyl group), a peak based on the carbons of the aromatic hydrocarbon group or the unsaturated heterocyclic group near δ110 to 150 ppm, and a peak based on the carbon of >C═O near δ160-170 ppm.

The compound of general formula [II] that can be used as a starting material in the above process can be produced, for example, by the following process.

A compound of general formula [II] in which X is an oxygen atom may be produced by cyclizing a compound of the following formula [IV] ##STR29## wherein ##STR30## and R₁ are as defined in general formula [I]. The cyclization is carried out, for example, by heating the compound to a temperature of 160° to 220° C., or carrying out this heating by ultraviolet irradiation, or by bringing the compound into contact with a Lewis acid catalyst. The Lewis acid catalyst may be a known compound such as SnCl₄, TiCl₄, SbCl₅ and AlCl₃. The amount of the Lewis acid used is not particularly restricted, but usually amounts of 0.001 to 1 mole per mole of the compound to be cyclized are preferred.

A compound of general formula [II]]in which X is the group >N--R₃ may be produced by reacting the compound of general formula [IV] with an amine compound of the following general formula [V]

    H.sub.2 N--R.sub.3                                         [V]

wherein R₃ is as defined in general formula [I], to obtain an imide compound of the general formula [IV-a] ##STR31## wherein all symbols are as defined, and then cyclizing the imide compound under the same conditions as described above.

Furthermore, a compound of general formula [II] in which X is the group >N--R₃ can be obtained by reacting an imide compound represented by general formula [III] ##STR32## wherein ##STR33## and X are as defined in general formula [I], with an alkali metal, and then reacting the product with a bromine compound of general formula [VII]

    Br--R.sub.3                                                [VII]

wherein R₃ is as defined in general formula [I].

The compound of general formula [I] provided by this invention is well soluble in general organic solvents such as toluene, chloroform and tetrahydrofuran. When the compound [I] is dissolved in such a solvent, the solution has a reversible photochromic action such that it is almost colorless and transparent, and when sunlight or ultraviolet rays are irradiated onto it, it develops a color. Even when the light is shut off, its coloration hardly changes at ordinary temperature. When it is heated to about 80° C., the state of coloration is stable and it does not return to its original colorless form. However, when white light is irradiated, it rapidly attains the original colorless form. The compound of formula [I] also exhibits this photochromic action in a polymeric solid matrix with a reversing speed on the order of seconds. A polymer for forming such a polymeric material may be any polymer in which the compound [I] can be dispersed uniformly. The molecular weight of the polymer is selected from 500 to 500,000. Examples of optically desirable polymers include polymethyl acrylate, polyethyl acrylate, polymethyl methacrylate, polyethyl methacrylate, polystyrene, polyacrylonitrile, polyvinyl alcohol, polyacrylamide, poly(2-hyroxyethyl methacrylate), polydimethylsiloxane, polycarbonate and poly(allyl diglycol carbonate); and copolymers obtained by copolymerizing the monomers constituting the above polymers either with each other or with other monomers.

The amount of the compound [I] to be dispersed in the above polymer is generally 0.001 to 70 parts by weight, preferably 0.005 to 30 parts by weight, especially preferably 0.1 to 15 parts by weight, per 100 parts by weight of the polymer.

The compounds represented by general formula [I] generally exist as colorless to pale yellow crystalline solids at room temperature and atmospheric pressure. The crystalline solids themselves have photochromism. When a crystalline solid of the compound of general formula [I] is irradiated with light containing ultraviolet rays, its coloration does not change at all at room temperature even if the light is shut off. Furthermore, when it is heated to about 80° C., the state of coloration is stable and it does not return to the original colorless form. But when white light is irradiated, it rapidly returns to its original colorless form reversibly, thus showing photochromism. Furthermore, the colored form of the photochromic compounds of this invention is thermally stable as compared with conventional fulgide compounds, and hardly returns to its original colorless form at about 80° C. When white light is irradiated, the colored form rapidly returns to its original colorless form reversibly. This repeated changes have excellent durability.

Accordingly, the compounds of this invention can be broadly utilized as a photochromic material. For example, they can be utilized in various recording materials superseding silver salt photographic materials, for example in memory materials, printing photographic materials, recording materials for a cathode ray tube, photographic materials for laser and photographic materials for holography. The photochromic material containing the compound of this invention can also be utilized as a photochromic lens material, an optical filter material, a display material, an actinometer, or a decorative material.

The photochromic compounds represented by general formula [I] show photochromism in solution or in a polymeric solid matrix, or their crystals themselves show photochromism. These compounds in a general condition are stably colorless or pale yellow, and immediately develop a color upon irradiation of ultraviolet rays. Even when the ultraviolet irradiation is stopped, their colored state is thermally stable even at 80° C., and when white light is irradiated, it rapidly returns to its colorless form. They also have the property of repeating these color changes.

In general formula [I], R₂ is the above-specified substituents and not a hydrogen atom. Compounds of general formula [I] in which R₂ is the specified substituents have good thermal stability in the colored state, and return to their original colorless form only when white light is irradiated. They repeat these color changes with good durability. This is clear from the fact that in the following Examples and Comparative Examples, the photochromic properties of the compounds of this invention in which R₂ represents hydrocarbon groups which may have various substituents had better photochromic properties (thermal stability and durability of color density) than compounds of formula [I] in which R₂ is a hydrogen atom.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is the proton nuclear magnetic resonance spectrum of the product obtained in Example 1;

FIG. 2 is the proton nuclear magnetic resonance spectrum of the product obtained in Example 2; and

FIG. 3 is the proton nuclear magnetic resonance spectrum of the product obtained in Example 5.

The following examples illustrate the present invention in greater detail without limiting the invention thereby.

EXAMPLE 1

A compound of the following formula (3.4 g; 0.01 mole) ##STR34## was dissolved in 100 cc of N,N-dimethylformamide, and 13.8 g (0.1 mole) of potassium carbonate and 14.1 g (0.1 mole) of methyl iodide were added. They were reacted at room temperature for 72 hours to give a fulgide compound (1) of the following formula. This compound was purified by chromatography on silica gel using chloroform and hexane as an eluent, and obtained in a yield of 17% as pale yellow crystals from ether. The elemental analysis values of this compound were C 70.92%, H 6.32%, O 12.79% and S 9.97% which very well agreed with C 71.16%, H 6.26%, O 13.54%, S 9.04% calculated for C₂₁ H₂₂ O₃ S. Its proton nuclear magnetic resonance spectrum showed a peak of 2H based on the protons of the thiophene ring near δ7.0-7.5 ppm, a peak of 3H based on the protons of --CH₃ bond near δ2.7 ppm, a peak of 3 H based on the protons of the methyl group of the reacted methyl iodide near δ1.3 ppm, and a peak of 14H based on the protons of the adamantylidene group near δ1.3-2.5 ppm.

The ¹³ C-nuclear magnetic resonance spectrum of this compound showed a peak based on the carbons of the adamantylidene group near δ27-50 ppm, a peak based on the carbon of the methyl group near δ15-20 ppm, a peak based on the carbon atoms of the thiophene ring near δ110-160 ppm and a peak based on the carbon of the >C═O near δ160-170 ppm (see FIG. 1).

The above results led to the determination that the isolated product is a photochromic compound (1) of the following structural formula. ##STR35##

EXAMPLE 2

A fulgide compound of the following formula (3.0 g; 0.01 mole) ##STR36## was dissolved in tetrahydrofuran, and reacted with 1 9 of potassium at room temperature to give 2.5 g of the following compound. ##STR37##

This compound was reacted with 7.1 g (0.05 mole) of methyl iodide in N-mehylpyrrolidone to form a photochromic compound (2) below. It was purified by chromatography on silica gel using dichloromethane as an eluent, and obtained in a yield of 21.2% as pale yellow crystals from ether. The elemental analysis values of this compound were C 68.63%, H 5.81%, 0 15.21%, S 10.36% which well agreed with C 68.79%, H 5.73%, O 15.27% and S 10.20% calculated for C₁₈ H₁₈ O₃ S. Its proton nuclear magnetic resonance spectrum showed a peak of 2H based on the protons of the thiophene ring near δ7.0-7.5 ppm, a peak of 3H based on the proton of the --CH₃ bond near δ2.66 ppm, a peak of 3H based on the proton of the reacted methyl group near δ1.3 ppm, and a peak of 10H based on the protons of the norbornylidene group near δ 1.5-2.0 ppm (see FIG. 2).

Its ¹³ C-nuclear magnetic resonance spectrum showed a peak based on the carbons of the norbornylidene group near δ20-45 ppm, a peak based on the carbon of the methyl group near δ15-20 ppm, a peak based on the carbons of the thiophene ring near δ110-160 ppm and a peak based on the carbon of the >C═O bond near δ160-170 ppm.

The above results led to the determination that the isolated product is a photochromic compound (2) of the following formula. ##STR38##

EXAMPLE 3

A fulgide compound of the following formula (3.39 g; 0.01 mole) ##STR39## was dissolved in 100 cc of dimethyl sulfoxide and 212 g (0.2 mole) of sodium carbonate and 30.6 g (0.2 mole) of methyl bromoacetate were added. They were reacted at room temperature for 70 hours to give a fulgide compound (3) of the formula given below. This compound was purified by chromatography on silica gel using dichloromethane as an eluent and obtained in a yield of 15.3% as pale yellow crystals from ether and hexane. The elemental analysis values of this compound were C 64.52%, H 6.03%, N 2.88%, O 20.1% and S 6.47% which very well agreed with C 64.60%, H 6.00%, N 2.90%, O 19.86%, S 6.63% calculated for C₂₆ H₂₉ NO₆ S. Its proton nuclear magnetic resonance spectrum showed a peak of 2H based on the protons of the thiophene ring near δ7.0-7.5 ppm, a peak of 3H based on the protons of --CH₃ near δ 2.60 ppm, two peaks of 6H based on the methyl group bonded to ##STR40## bond near δ3.4-3.8, a peak of 2H based on the methylene group in the ##STR41## bond near δ4.4, a peak of 2H based on the methylene group of the ##STR42## bond near δ3.0 ppm and a peak of 14H based on the protons of the adamantylidene group near δ1.5-2.0 ppm (see FIG. 3).

When its ¹³ C-nuclear magnetic resonance spectrum was measured, a peak based on the carbon atoms of the adamantylidene group appeared near δ27-50 ppm; a peak based on the carbon of the methyl group of the ##STR43## near δ50-60 ppm; a peak based on the carbons of the thiophene ring, near δ110-160 ppm; a peak based on the carbon of the >C═O bond, near 160-180 ppm; a peak based on the carbon of --CH₃, near δ15 ppm; and a peak based on the carbon of the methylene group of the ##STR44## bond, near δ50-60 ppm.

The above results led to the determination that the isolated product is a photochromic compound (3) of the following structural formula ##STR45##

EXAMPLES 4-50

In the same way as in Examples 1 to 3, photochromic compounds were synthesized from the materials shown in Table 1-A.

The elemental analysis values, proton nuclear magnetic resonance spectra, ¹³ C-nuclear magnetic resonane spectra of the resulting compounds were measured, and they were identified as compounds having the structural formulae (4) to (59) shown in Table 1-A. The elementral analysis values of the resulting compounds are shown in Table 1-B.

    TABLE 1-A       No. Starting material product Yield (%)       4      ##STR46##       ##STR47##       19       5      ##STR48##       ##STR49##       20       6      ##STR50##       ##STR51##       21       7      ##STR52##       ##STR53##       20       8      ##STR54##       ##STR55##       21       9      ##STR56##       ##STR57##       25       10      ##STR58##       ##STR59##       24       11      ##STR60##       ##STR61##       23       12      ##STR62##       ##STR63##       16       13      ##STR64##       ##STR65##       19       14      ##STR66##       ##STR67##       25       15      ##STR68##       ##STR69##       21       16      ##STR70##       ##STR71##       19       17      ##STR72##       ##STR73##       23       18      ##STR74##       ##STR75##       20       19      ##STR76##       ##STR77##       22       20      ##STR78##       ##STR79##       17       21      ##STR80##       ##STR81##       21       22      ##STR82##       ##STR83##       22       23      ##STR84##       ##STR85##       19       24      ##STR86##       ##STR87##       18       25      ##STR88##       ##STR89##       21       26      ##STR90##       ##STR91##       24       27      ##STR92##       ##STR93##       18       28      ##STR94##       ##STR95##       16       29      ##STR96##       ##STR97##       19       30      ##STR98##       ##STR99##       21       31      ##STR100##       ##STR101##       20       32      ##STR102##       ##STR103##       20       33      ##STR104##       ##STR105##       19       34      ##STR106##       ##STR107##       21       35      ##STR108##       ##STR109##       20       36      ##STR110##       ##STR111##       20       37      ##STR112##       ##STR113##       21       38      ##STR114##       ##STR115##       20       39      ##STR116##       ##STR117##       22       40      ##STR118##       ##STR119##       19       41      ##STR120##       ##STR121##       20       42      ##STR122##       ##STR123##       18       43      ##STR124##       ##STR125##       21       44      ##STR126##       ##STR127##       19       45      ##STR128##       ##STR129##       20       46      ##STR130##       ##STR131##        18       47      ##STR132##       ##STR133##       22       48      ##STR134##       ##STR135##       17       49      ##STR136##       ##STR137##       23       50      ##STR138##       ##STR139##       19       51      ##STR140##       ##STR141##       21       52      ##STR142##       ##STR143##       18       53      ##STR144##       ##STR145##       20       54      ##STR146##       ##STR147##       19       55      ##STR148##       ##STR149##       19       56      ##STR150##       ##STR151##       21       57      ##STR152##       ##STR153##       19       58      ##STR154##       ##STR155##       20       59      ##STR156##       ##STR157##       20

                                      TABLE 1-B                                    __________________________________________________________________________     Elemental analysis (%)                                                         Calculated             Found                                                   No.                                                                               C  H  N  O  S  Others                                                                              C  H  N  O  S  Others                                   __________________________________________________________________________      4 78.65                                                                             6.37                                                                              --  8.99                                                                             5.99                                                                              --   78.42                                                                             6.47                                                                              --  9.01                                                                             6.10                                                                              --                                        5 60.12                                                                             4.47                                                                              --  8.59                                                                             5.73                                                                              Br                                                                               14.30                                                                             60.21                                                                             4.52                                                                              --  8.63                                                                             5.65                                                                              Br                                                                               14.24                                                    F  6.80             F  6.79                                   6 70.83                                                                             7.29                                                                              2.43                                                                              13.89                                                                             5.56                                                                              --   70.72                                                                             7.33                                                                              2.46                                                                              13.82                                                                             5.67                                                                              --                                        7 72.20                                                                             6.75                                                                              --  8.75                                                                             5.83                                                                              Cl                                                                                6.46                                                                             72.29                                                                             6.71                                                                              --  8.81                                                                             5.72                                                                              Cl                                                                                6.47                                   8 79.32                                                                             7.12                                                                               --                                                                               13.56                                                                             -- --   79.38                                                                             7.09                                                                              -- 13.52                                                                             -- --                                        9 71.97                                                                             6.16                                                                              -- 10.37                                                                             -- Cl                                                                               11.49                                                                             71.89                                                                             6.24                                                                              -- 10.42                                                                             -- Cl                                                                               11.45                                  10 70.46                                                                             6.42                                                                              2.57                                                                              14.68                                                                             5.87                                                                              --   70.41                                                                             6.49                                                                              2.62                                                                              14.73                                                                             5.75                                                                              --                                       11 58.69                                                                             3.54                                                                              -- 10.79                                                                             5.40                                                                              Cl                                                                               11.96                                                                             58.60                                                                             3.58                                                                              -- 10.72                                                                             5.43                                                                              Cl                                                                               11.94                                                    F  9.61             F  9.73                                  12 75.45                                                                             5.99                                                                              4.19                                                                              14.37                                                                             -- --   75.41                                                                             5.92                                                                              4.24                                                                              14.43                                                                             -- --                                       13 62.31                                                                             5.19                                                                              2.14                                                                               7.33                                                                             -- Cl                                                                               10.83                                                                             62.37                                                                             5.14                                                                              2.09                                                                               7.37                                                                             -- Cl                                                                                10.80                                                   Br                                                                               12.20             Br                                                                               12.23                                  14 67.50                                                                             6.52                                                                              -- 18.00                                                                             -- Cl                                                                                7.98                                                                             67.51                                                                             6.46                                                                              -- 17.93 Cl                                                                                8.10                                  15 76.43                                                                             6.37                                                                              2.97                                                                              10.19                                                                             -- F  4.03                                                                             76.49                                                                             6.32                                                                              2.93                                                                              10.24                                                                             -- F  4.02                                  16 69.57                                                                             5.41                                                                              2.71                                                                               9.28                                                                             6.18                                                                              Cl                                                                                6.85                                                                             69.64                                                                             5.43                                                                              2.66                                                                               9.24                                                                             6.17                                                                              Cl                                                                                6.86                                  17 59.73                                                                             4.98                                                                              6.33                                                                              21.72                                                                             7.24                                                                              --   59.67                                                                             4.93                                                                              6.40                                                                              21.64                                                                             7.36                                                                              --                                       18 64.88                                                                             5.24                                                                              7.10                                                                              10.81                                                                             -- Cl                                                                               11.98                                                                             64.79                                                                             5.29                                                                              7.04                                                                              10.83                                                                             -- Cl                                                                               12.05                                  19 72.58                                                                             7.26                                                                              2.82                                                                               9.68                                                                             -- F  7.66                                                                             72.54                                                                             7.24                                                                              2.78                                                                               9.74                                                                             -- F  7.70                                  20 75.98                                                                             6.15                                                                              -- 11.92                                                                             5.96                                                                              --   75.92                                                                             6.18                                                                              -- 11.94                                                                             5.95                                                                              --                                       21 60.92                                                                             4.76                                                                              2.22                                                                              10.15                                                                             5.08                                                                              Cl                                                                                16.87                                                                            60.90                                                                             4.78                                                                              2.19                                                                              10.17                                                                             5.11                                                                              Cl                                                                               16.85                                  22 79.72                                                                             6.29                                                                              --  8.39                                                                             5.59                                                                              --   79.68                                                                             6.31                                                                              --  8.36                                                                             5.64                                                                              --                                       23 62.85                                                                             5.07                                                                              2.37                                                                              10.81                                                                             5.41                                                                              Br                                                                               13.50                                                                             62.83                                                                             5.09                                                                              2.34                                                                              10.84                                                                             5.41                                                                              Br                                                                               13.50                                  24 71.68                                                                             6.17                                                                              -- 18.50                                                                             -- F  3.66                                                                             71.64                                                                             6.14                                                                              -- 18.56                                                                             -- F  3.67                                  25 67.40                                                                             5.25                                                                              --  8.70                                                                             5.80                                                                              Cl                                                                               12.85                                                                             64.36                                                                             5.29                                                                              --  8.74                                                                             5.76                                                                              Cl                                                                               12.85                                  26 69.55                                                                             4.52                                                                              1.98                                                                              13.57                                                                             -- Cl                                                                                5.01                                                                             69.52                                                                             4.56                                                                              1.96                                                                              13.52                                                                             -- Cl                                                                                5.05                                                    F  5.37             F  5.39                                  27 57.53                                                                             5.37                                                                              2.68                                                                              21.48                                                                             6.14                                                                              Cl                                                                                6.80                                                                             57.50                                                                             5.34                                                                              2.72                                                                              21.47                                                                             6.17                                                                              Cl                                                                                6.80                                  28 73.00                                                                             5.70                                                                              -- 15.21                                                                             6.08                                                                              --   72.96                                                                             5.72                                                                              -- 15.24                                                                             6.07                                                                              --                                       29 76.86                                                                             7.96                                                                              2.72                                                                              12.43                                                                             -- --   76.82                                                                             7.97                                                                              2.76                                                                              12.42                                                                             -- --                                       30 75.67                                                                             5.66                                                                              -- 12.94                                                                             -- Cl                                                                                5.73                                                                             75.62                                                                             5.69                                                                              -- 12.97                                                                             -- Cl                                                                                5.74                                  31 75.52                                                                             6.85                                                                              1.96                                                                              11.19                                                                             4.48                                                                              --   75.47                                                                             6.86                                                                              1.99                                                                              11.17                                                                             4.51                                                                              --                                       32 72.80                                                                             7.11                                                                              -- 13.39                                                                             6.69                                                                              --   72.84                                                                             7.12                                                                              -- 13.35                                                                             6.68                                                                              --                                       33 73.72                                                                             6.14                                                                              -- 13.65                                                                             -- F  6.48                                                                             73.69                                                                             6.12                                                                              -- 13.69                                                                             -- F  6.49                                  34 78.42                                                                             6.99                                                                              -- 14.59                                                                             -- --   78.39                                                                             7.01                                                                              -- 14.60                                                                             -- --                                       35 72.45                                                                             6.42                                                                              -- 15.09                                                                             6.04                                                                              --   72.41                                                                             6.46                                                                              -- 15.07                                                                             6.06                                                                              --                                       36 77.95                                                                             5.74                                                                              4.23                                                                              12.08                                                                             -- --   77.92                                                                             5.76                                                                              4.24                                                                              12.08                                                                             -- --                                       37 72.79                                                                             6.62                                                                              -- 14.71                                                                             5.88                                                                              --   72.73                                                                             6.60                                                                              -- 14.76                                                                             5.91                                                                              --                                       38 64.21                                                                             4.61                                                                              -- 14.76                                                                             5.90                                                                              F 10.52                                                                             64.18                                                                             4.64                                                                              -- 14.74                                                                             5.93                                                                              F 10.51                                  39 73.12                                                                             6.81                                                                              -- 14.34                                                                             5.73                                                                              --   73.09                                                                             6.78                                                                              -- 14.38                                                                             5.75                                                                              --                                       40 69.29                                                                             6.04                                                                              3.67                                                                              21.00                                                                             -- --   69.32                                                                             6.07                                                                              3.62                                                                              20.99                                                                             -- --                                       41 67.94                                                                             4.72                                                                              2.20                                                                              12.58                                                                             -- Br                                                                               12.56                                                                             67.87                                                                             4.69                                                                              2.28                                                                              12.61                                                                             -- Br                                                                               12.55                                  42 79.02                                                                             6.58                                                                              2.14                                                                              12.60                                                                             -- --   79.07                                                                             6.54                                                                              2.17                                                                              12.56                                                                             -- --                                       43 54.79                                                                             4.06                                                                              -- 16.23                                                                             5.41                                                                              Cl                                                                                5.99                                                                             54.83                                                                             4.09                                                                              -- 16.17                                                                             5.42                                                                              Cl                                                                                5.96                                                    Br                                                                               13.51             Br                                                                               13.52                                  44 73.35                                                                             7.58                                                                              3.42                                                                               7.82                                                                             7.82                                                                              --   73.27                                                                             7.59                                                                              3.46                                                                               7.86                                                                             7.81                                                                              --                                       45 81.36                                                                             6.97                                                                              2.64                                                                               9.04                                                                             -- --   81.33                                                                             6.99                                                                              2.66                                                                               9.05                                                                             -- --                                       46 75.95                                                                             5.54                                                                              4.43                                                                               5.06                                                                             -- F  9.02                                                                             75.92                                                                             5.50                                                                              4.46                                                                               5.07                                                                             -- F  9.05                                  47 63.75                                                                             7.33                                                                              2.56                                                                               5.86                                                                             5.86                                                                              Br                                                                               14.64                                                                             63.72                                                                             7.30                                                                              2.59                                                                               5.88                                                                             5.89                                                                              Br                                                                               14.62                                  48 81.62                                                                             7.09                                                                              2.03                                                                               4.63                                                                             4.63                                                                              --   81.60                                                                             7.07                                                                              2.06                                                                               4.61                                                                             4.66                                                                              --                                       49 74.94                                                                             5.72                                                                              4.86                                                                               8.33                                                                             -- Cl                                                                                6.15                                                                             74.91                                                                             5.73                                                                              4.88                                                                               8.30                                                                             -- Cl                                                                                6.18                                  50 62.44                                                                             5.88                                                                              6.33                                                                              18.10                                                                             7.24                                                                              --   62.47                                                                             5.86                                                                              6.31                                                                              18.07                                                                             7.28                                                                              --                                       51 71.29                                                                             6.93                                                                              2.77                                                                              12.67                                                                             6.34                                                                              --   71.29                                                                             6.96                                                                              2.73                                                                              12.61                                                                             6.41                                                                              --                                       52 72.37                                                                             5.78                                                                              1.76                                                                              10.05                                                                             -- Br                                                                               10.04                                                                             72.33                                                                             5.81                                                                              1.77                                                                              10.01                                                                             -- Br                                                                               10.08                                  53 79.43                                                                             6.98                                                                              5.01                                                                               8.59                                                                             -- --   79.40                                                                             6.99                                                                              5.03                                                                               8.59                                                                             -- --                                       54 67.32                                                                             4.73                                                                              4.91                                                                              11.22                                                                             5.61                                                                              Cl                                                                                6.21                                                                             67.36                                                                             4.70                                                                              4.90                                                                              11.17                                                                             5.64                                                                              Cl                                                                                6.23                                  55 58.69                                                                             3.71                                                                              9.45                                                                              10.79                                                                             5.40                                                                              Cl                                                                               11.96                                                                             58.66                                                                             3.70                                                                              9.47                                                                              10.83                                                                             5.36                                                                              Cl                                                                               11.98                                  56 61.06                                                                             5.97                                                                              6.19                                                                               7.08                                                                             7.08                                                                              F 12.61                                                                             61.02                                                                             5.99                                                                              6.21                                                                               7.06                                                                             7.09                                                                              F 12.62                                  57 76.51                                                                             5.54                                                                              1.94                                                                              11.09                                                                             -- Cl                                                                                4.91                                                                             76.58                                                                             5.48                                                                              1.91                                                                              11.12                                                                             -- Cl                                                                                4.90                                  58 70.42                                                                             7.51                                                                              3.29                                                                              11.27                                                                             7.51                                                                              --   70.38                                                                             7.49                                                                              3.32                                                                              11.26                                                                             7.55                                                                              --                                       59 66.42                                                                             7.38                                                                              2.58                                                                              17.71                                                                             5.90                                                                              --   66.44                                                                             7.36                                                                              2.56                                                                              17.73                                                                             5.90                                                                              --                                       __________________________________________________________________________

EXAMPLES 60-118

In each run, 0.5 part by weight of each of the compounds (1) to (59) produced in Examples 1 to 59 and 10 parts by weight of poly(methyl methacrylate) were dispersed in 100 parts by weight of benzene, and the dispersion was cast onto a slide glass (11.2×3.7 cm) to form a film having a thickness of 0.1 mm. The durability of this photochromic film in the repetition of color formation and extinction (repetitive durability) was measured under the conditions described below.

Excitation light source: Xenon lamp (250 W); Irradiation time 3 seconds

Color extinction light source: Xeon lamp (250 W; light of a wavelength 400 nm and below was cut off by providing a filter); Irradiation time 30 seconds.

The repetitive durability was defined as the number of repetitions of color formation-extinction which was required for the initial color density of the film to decrease to half.

Furthermore, light from the above excitation light source was irradiated on the above film, and the color density of the film measured at this time was made an initial density. The film was put in an oven at 80° C., and the thermal stability of the formed color of the film was evaluated. The thermal stability was defined as the time required for the above initial density value to decrease to half.

The results are shown in Table 2.

For Comparison, films were prepared as above using compounds (60) and (61) below, and their durability and thermal stability were measured. ##STR158##

                  TABLE 2                                                          ______________________________________                                                                           Thermal                                                Photochromic  Number of stability                                    Example No.                                                                              compound No.  repetitions                                                                              (hours)                                      ______________________________________                                         60         1            3000      1200                                         61         2            2800       900                                         62         3            3500      1000                                         63         4            3300      1210                                         64         5            3100      1250                                         65         6            2900      1200                                         66         7            2950      1230                                         67         8            3230      1190                                         68         9            3110      1180                                         69        10            3380      1210                                         70        11            3210      1190                                         71        12            3300      1150                                         72        13            2900       880                                         73        14            2950       920                                         74        15            2850       900                                         75        16            3150       850                                         76        17            3050       800                                         77        18            3000       900                                         78        19            3250       900                                         79        20            2950      1250                                         80        21            3110      1200                                         81        22            3120      1200                                         82        23            3400       820                                         83        24            3380      1190                                         84        25            2780       830                                         85        26            3130      1200                                         86        27            3190       900                                         87        28            3090      1220                                         88        29            3120      1250                                         89        30            2850      1200                                         90        31            2960      1210                                         91        32            3010      1190                                         92        33            3020      1250                                         93        34            3030      1200                                         94        35            3010      1200                                         95        36            2880      1180                                         96        37            2980      1190                                         97        38            3110      1210                                         98        39            3120      1200                                         99        40            3220      1250                                         100       41            2980      1200                                         101       42            3100      880                                          102       43            3000      880                                          103       44            3240      1130                                         104       45            2930      1190                                         105       46            2810      1100                                         106       47            2790       820                                         107       48            2860      1150                                         108       49            3080       840                                         109       50            3060      1090                                         110       51            3030      1130                                         111       52            3010       880                                         112       53            3120      1100                                         113       54            2880      1100                                         114       55            2970      1150                                         115       56            2780       850                                         116       57            3100      1120                                         117       58            3000       860                                         118       59            3360      1100                                         Comparison 1                                                                             (60)           500      2 (sec.)                                     Comparison 2                                                                             (61)           300       250                                         ______________________________________                                     

We claim:
 1. A compound represented by the following formula [I] ##STR159## wherein ##STR160## represents a divalent benzene ring, a divalent naphthalene ring, a divalent 5-membered monoheterocyclic group having one hetero atom, or a fused heterocyclic group resulting from fusion of a benzene ring to said monoheterocyclic group, each of which may be substituted by at least one atom or group selected from the group consisting of halogen atoms, nitro groups, cyano groups, C₁ -C₄ alkyl groups, C₁ C₄ alkoxy groups, C₁ -C₄ alkylamino groups, di(C₁ -C₄)alkylamino groups, phenyl groups and C₁ -C₄ alkoxyphenyl groups, and when two alkyl groups are substituted on each said ring, they may be bonded to each other to form a ring,R₁ represents a C₁ -C₆ alkyl group which may be substituted by a halogen atom or a C₁ -C₄ alkoxy group; a C₇ -C₁₀ aralkyl group may be substituted by a halogen atom; a C₆ -C₁₀ aryl group which may be substituted by a halogen atom, a nitro group or a C₁ -C₄ alkoxy group; ##STR161## represents a norbornylidene or adamantylidene group which may be substituted by at least one atom or group selected from the group consisting of hydroxyl groups, nitro groups, cyano groups, carboxyl groups, halogen atoms, C₁ -C₄ alkylamino groups, di(C₁ -C₄) alkylamino groups, C₁ -C₄ alkyl groups, C₁ -C₄ alkoxy groups, C₁ -C₂ haloalkyl groups, C₂ -C₁₀ alkoxycarbonyl groups, (C₁ -C₄)alkylcarbonyl(C₁ -C₄)alkyl groups, C₇ -C₁₅ aralkyl groups, C₇ -C₁₅ aralkoxy groups, C₆ -C₁₀ aryl groups and C₆ -C₁₀ aryloxy groups, X represents an oxygen atom or the group >N--R₃ wherein R₃ represents a C₁ -C₆ alkyl group, a C₅ -C₇ cycloalkyl group, a C₇ -C₁₀ aralkyl group or a C₆ -C₁₀ aryl group, each of which may be substituted by at least one atom or group selected from the group consisting of halogen atoms, cyano groups, nitro groups, hydroxyl groups, C₁ -C₅ alkoxy groups, C₆ -C₁₀ aryloxy groups, ##STR162## wherein R₄ represents a C₁ -C₄ alkyl group or a C₆ -C₁₀ aryl group each of which may be substituted by a halogen atom, R₅ represents a C₁ -C₄ alkyl group which may be substituted by a halogen atom or a nitro group, or a C₆ -C₁₀ aryl group or a C₇ -C₁₀ aralkyl group each of which may be substituted by a cyano group, and R₆ and R₇ are identical or different and each represents a hydrogen atom, a C₁ -C₄ alkyl group, a C₇ -C₁₀ aralkyl group or a C₆ -C₁₀ aryl group, and R₂ represents a C₁ -C₆ alkyl group, a C₅ -C₇ cycloalkyl group, a (C₅ -C₇)cycloalkyl(C₁ -C₄)alkyl group or a C₇ -C₁₀ aralkyl group, each of which may be substituted by at least one atom or group selected from the group consisting of halogen atoms, cyano groups, nitro groups, hydroxyl groups, C₁ -C₆ alkoxy groups, C₆ -C₁₀ aryloxy groups optionally substituted by a halogen atom, C₇ -C₁₅ aralkoxy groups, ##STR163## wherein R₄ represents a C₁ -C₄ alkyl group which may be substituted by a halogen atom, R₅ represents a C₁ -C₄ alkyl group which may be substituted by a cyano group, and R₆ and R₇ are identical or different and each represents a hydrogen atom, a C₁ -C₄ alkyl group, a C₇ -C₁₀ aralkyl group or a C₆ -C₁₀ aryl group.
 2. The compound of claim 1 in which X in formula [I] is an oxygen atom.
 3. The compound of claim 1 in which X in formula [I] is the group >N--R₃ wherein R₃ represents a C₁ -C₆ alkyl group, a C₅ -C₇ cycloalkyl group, a C₇ -C₁₀ aralkyl group or a C₆ -C₁₀ aryl group, each of which may be substituted by at least one atom or group selected from the class consisting of halogen atoms, cyano groups, nitro groups, hydroxyl groups, C₁ -C₅ alkoxy groups, C₆ -C₁₀ aryloxy groups, ##STR164## wherein R₄ represents a C₁ -C₄ alkyl group or a C₆ 14 C₁₀ aryl group each of which may be substituted by a halogen atom, R₅ represents a C₁ -C₄ alkyl group which may be substituted by a halogen atom or a nitro group, or a C₆ -C₁₀ aryl group or a C₇ -C₁₀ aralkyl group each of which may be substituted by a cyano group, and R₆ and R₇ are identical or different and each represents a hydrogen atom, a C₁ -C₄ alkyl group, a C₇ -C₁₀ aralkyl group or a C₆ -C₁₀ aryl group.
 4. The compound of claim 1 in which X in formula [I] is the group >N--R₃ in which R₃ represents a C₁ -C₆ alkyl group, a C₅ -C₇ cycloalkyl group or a Chd 7-C₁₀ aralkyl group, each of which may be substituted by a halogen atom, a cyano group, a nitro group, a C₁ -C₆ alkoxy group or the ##STR165## wherein R₅ represents a C₁ -C₄ alkyl group which may be substituted by a halogen atom or a nitro group, or a C₆ -C₁₀ aryl group which may be substituted by a cyano group.
 5. The compound of claim 1 in which ##STR166## in formula [I] represents an adamantylidene group which may have a substituent.
 6. The compound of claim 1 in which in formula [I], ##STR167## represents an adamantylidene group which may have a substituent, and X is an oxygen atom.
 7. The compound of claim 1 in which ##STR168## in formula [I] represents an adamantylidene or norbornylidene group substituted by at least one atom or group selected from the class consisting of halogen atoms, C₁ -C₄ alkyl groups, C₁ -C₄ alkoxy groups, C₁ -C₄ alkylamino groups, di(C₁ -C₄)alkylamino groups and (C₁ -C₄)alkylcarbonyl(C₁ -C₄)alkyl groups.
 8. The compound of claim 1 in which R₁ in formula [I] represents a C₁ -C₆ alkyl group; a C₇ -C₁₀ aralkyl group; or a C₆ -C₁₀ aryl group which may be substituted by a halogen atom, a nitro group or a C₁ -C₄ alkoxy group.
 9. The compound of claim 1 in which ##STR169## in formula [I] represents a divalent benzene ring, a divalent naphthalene ring, a divalent furan ring, a divalent pyrrole ring, a divalent thiophene ring, a divalent benzofuran ring, a divalent indole ring, a divalent benzothiophene ring or a divalent tetrahydrobenzothiophene group, each of which may be substituted by an atom or group selected from the class consisting of halogen atoms, nitro groups, cyano groups, C₁ -C₄ alkyl groups, C₁ -C₄ alkoxy groups, C₁ -C₄ alkylamino groups, di(C₁ -C₄)alkylamino groups, phenyl groups and C₁ -C₄ alkoxyphenyl groups.
 10. The compound of claim 1 in which X represents an oxygen atom or the group >N--R₃ wherein R₃ represents a C₁ -C₆ alkyl group which may be substituted by a halogen atom, a cyano group, or a C₂ -C₅ alkoxycarbonyl group; ##STR170## represents a norbornylidene or adamantylidene group; R₁ represents a C₁ -C₄ alkyl group or a C₆ -C₁₀ aryl group; R₂ is a C₁ -C₄ alkyl group which may be substituted by a C₂ -C₅ alkoxycarbonyl group; and ##STR171## is a divalent furan ring, a divalent pyrrole ring or a divalent thiophene ring.
 11. A process for producing the compound of formula [I] according to claim 1, which comprises reacting a compound represented by the following formula [II] ##STR172## wherein ##STR173## and X are as defined in general formula [I], with a halogen compound represented by the following general formula [III]

    Hal--R.sub.2                                               [III]

wherein Hal represents a chloride, bromine or iodine atom, and R₂ is as defined in formula [I] in claim 1,in the presence of an alkali metal or an alkali metal carbonate or after the compound of formula [I] is reacted with the alkali metal or its carbonate.
 12. A photochromic composition comprising the compound of formula [I] according to claim 1 and a polymer.
 13. The composition of claim 12 wherein the amount of the compound of formula [I] is 0.001 to 70 parts by weight per 100 parts by weight of the polymer.
 14. A photomemory material composed of the composition of claim
 12. 